1. Field of the Invention
The present invention relates to farm machinery and more particularly to disc-type tillage equipment.
2. Description of the Prior Art
Prior to this device disc-type tillage devices had many disadvantages such as: they could turn in only one direction while working the ground, or could not be turned at all without raising the device; larger disc devices had a large width to depth ratio so they did not follow changes in ground elevation well; they could only be operated in one direction when trying to get close to an obstacle such as a fence or did not till the ground well near an obstacle; when operated in the direction necessary to get close to an object they often left ridges; and an inexperienced or inattentive operator could easily damage the device by turning or crossing a ditch or ridge.
Traditionally disc-type tillage devices have had two different configurations. One type of disc device is the offset disc which has rows of disc gangs arranged in a V shape, and the other type of disc device is known as the conventional or tandem disc, which has rows of disc gangs arranged in an X shape. With either type, the disc gangs are suspended from a frame which may be connected to a farm tractor, bull dozer or the like.
The offset disc has a row of front discs and a rear row of discs. (The individual discs sometimes being referred to as blades). Each disc or blade is cupped and rotates along a central axis. As the device is pulled, the front row of blades cut the ground and throws it out while the rear row of blades re-cuts the ground and moves it back to about its original position. This type of disc device may only be turned in one direction while in the ground without causing the front blades on the inside of the turn to dig in too deeply. If the blades are allowed to dig in, they will create a ridge and may bend or break. Since, by convention, the rows of blades converge on the left side the offset disc will allow a left-hand turn, but requires lifting out of the ground for a right-hand turn.
The other type of disc device is the conventional disc (sometimes referred to as a tandem) which may generally be designed with a greater width, but has many similar disadvantages. As the conventional disc is pulled over the ground the two rows of front blade gangs (the ones nearest the tractor) cut the ground and throw it outwardly away from the center of the device and then the rear blade gangs re-cut the ground and move it inwardly toward the center of the device. Thus, the ground is tilled and left in generally the same location as it was originally.
This arrangement of gangs is suitable if one is working level ground and traveling straight. However, with an implement of suitable width (left to right) for today's large tractors, the depth (front to rear) is such that when one crosses unlevel ground such as a ditch, the wheels and the blades near the center of the device leave the ground. This not only leaves ground in the bottom of the ditch untilled but also causes the weight of the device to be concentrated on the outer most blades so that they dig in leaving ridges, and possibly even damaging the device. The smaller the depth the less this is a problem, but with the arrangement of the gangs on this type of device, the depth increases significantly as the device gets wider thereby greatly intensifying the problem.
Similarly when one tries to turn the conventional disc device without raising it, the device will tend to pivot around the wheel to the inside of the turn causing the blades on the inside front of the device be pushed considerably against their cup shape. As a result, these blades will cut deeply into the ground and leave a ridge. In a turn such as this it is common for the blades to be bent or broken.